This project will yield a powerful tool for researchers mapping the human brain's functions with its spatially distinct parts. The work will build on existing Current Designs' fiber optic response pad ("fORP") technology. Fiber optic response pads are "button boxes that are specially constructed to allow people to respond to questions or other stimuli while being imaged in magnetic resonance imaging systems. They are essential in answering: "What brain activity do we observe (through MR imaging) at the instant when the subject pressed the button?" As this field advances, the accuracy of timing has become increasingly important. No commercially available system addresses the need. This project would extend the performance of the existing :FORP", and integrate it with freely available software, to provide a "Hard-Real-Time Stimulus/Response System" having the unique new qualities of sub-millisecond overall timing accuracy, low cost, and compatibility with magnetic resonance (MR) scanner environments. As a last step, the actual timing performance of the combined system will be characterized over a large number of trials. The resulting system will be an unparalleled stimulus/response system providing high value to researchers at low cost.